1. Field of the Invention
This invention relates to means for advancing an original document past the viewing station of a copying machine or the like.
2. Description of the Prior Art
In processing machines such as xerographic copiers and the like, it is generally necessary to scan an original document and project its image into processing apparatus for making a duplicate copy thereof. In the past, this generally has been accomplished by either holding the document stationary while moving the scanning apparatus relative thereto or by placing the document on a movable platen for advancing it past a stationary scanning or viewing window. In either case, the moving member has to be returned to the initial starting point at the end of each scanning cycle. The return stroke is an unproductive motion characteristic of the prior art arrangements which reduces the overall efficiency of the machine operation. The time lost during the return stroke is particularly significant when multiple copies are made of a single document, the return stroke sometimes taking as much as twenty-five percent of the copy cycle operation time.
It is known to provide a cylinder for holding a single document, end-to-end, for rotating relative to a scanning apparatus, as shown for example in West German unexamined patent specification Nos. OS 25 55 037, filed Dec. 6, 1975 and laid open June 8, 1977. As there shown, a document is held against the periphery of a cylinder by a single clamp which engages the opposite ends of the document and holds them securely in a recessed channel provided in the cylinder, thus partially blocking the end edges of the original document while also potentially causing damage to these edges. A cylindrical document holder for supporting a transparent master is disclosed in West German unexamined patent specification Nos. OS 26 16 137, filed Apr. 13, 1976 and laid open Oct. 20, 1977. As there shown, the light source for illuminating the transparent master is located within the cylinder and projects light through the document during the scanning operation. The means for holding a transparency on the cylinder is not disclosed.
While the above holders do not necessarily require a return stroke during scanning operations, neither of these devices provides for a rotatable document carrier which may be easily and quickly loaded and unloaded for use with a standard office copier or the like.